This invention relates to a plug and more particularly to a plug finding particular utility as a casting mold plug and to a method for sealing a casting mold.
Relatively large dies are used to mold engine blocks, transmission housings, and other large die-cast parts out of aluminum. Such dies are made out of an exotic metal that is capable of retaining its solidity and shape at a temperature higher than the aluminum that is being cast in the die. The die has a series of passages that are used to conduct water or oil for heating and cooling the die. In the case of oil, the die is heated initially by the use of oil at a certain temperature being conducted through these passages and then later the same oil may be used to carry heat away from the die in an effort to maintain a consistent temperature of the die. In the case of water, the molten aluminum being injected into the die is relied upon to raise the die temperature to a working level. When the working temperature of the die is established, water flows through the die to carry away excess heat. During the manufacturing of the die, holes are drilled in the die to provide the necessary passages through which the oil or water will pass. Before the die can be used the holes must be plugged to retain the water or oil.
The passages in the die over a period of time become filled with debris so that it is desirable that the plugs that are used to seal the passages can be removed easily and conveniently and the passages cleaned out. Presently existing plugs for these passages have been found to fail over a period of time causing the water or oil to leak form the die. Because leaking from the die is not only wasteful and inefficient but can cause damage to the cast part, it is desirable that an improved means be provided for sealing the passages with plugs that do not leak after a period of use.
An alternative means of constructing the die would be to weld the plug in place but then the plug could not be removed in order to clean out the passages. The plugs must be easily removable. The plug openings are threaded NPT ports, that is, they are xe2x80x9cNational Pipe Threadxe2x80x9d ports. The plugs are screwed into these ports and have a screw thread on them for mating with the threading in the ports. Over a period of time it is found that these plugs begin to leak and come out of the tapered thread openings. What is needed is plug that will seat, remain sealed, will not leak and will not come out over a period of time while the die is in use and yet is removable when it is desired to clean out the passages. The sealing plug must be suitable for use for both media and ambient temperatures of 350xc2x0 F.
One embodiment of the plug of the invention might include an outwardly threaded first member having a bore therethrough. There is also provided a second member of resilient expandable material which has a cylindrical shape with a central opening. An outwardly threaded third member is received within the bore and extends through the central opening of the second member. Also there is provided an inwardly threaded disc threadedly received on the third member and having projections which extend therefrom into the second member. The second member is received between the first member and the disc whereby rotating the third member into the threads of the disc moves the disc toward the first member and squeezes and expands the second member.
Another embodiment of the invention involves a plug which includes a first piece which is externally threaded and has a tapped hole. There is also provided a second piece made out of resilient expandable material and having a tubular shape with a central opening. Finally a bolt having an enlarged head and a threaded shank extends through the central opening of the second piece and is threadedly received in the tapped hole. The bolt is rotatable relative to the first piece to move the head toward the first piece to compress and expand the second piece.
Still another embodiment of the invention involves a plug for a casting die which includes an outwardly threaded first member. There is also provided a resilient expandable second member mounted on said first member. Finally a threaded third member is mounted on said first member and connected to the second member for expanding the second member.
A further embodiment of the invention is a method for sealing the passage of a casting die which includes providing a first externally threaded member. A second resilient expandable member is mounted on the first member. The first and second members are inserted into the passage by threading the first member into threads in the passage and finally expanding the second member against the walls of the passage.